Cyclodimerization process

ABSTRACT

Vinylcyclobutanes are prepared by cyclocodimerizing a diene and a monoolefin, in liquid phase solution, in the presence of a catalyst system containing an organo-titanium compound.

United Stats Canneli [4 1 Sept. 19, 1972 1 1 CYCLODHMEREZATIGN POCESS [56] Refiflffinm c1 [72] Inventor: Lawrence G. Cannell, Berkeley, UNHED STATES PATENTS 1'1. 94707 1 Ca 3,258,501 6/1966 Cannell ..260/666 1 Asslgneei Shell, Oil Company, New York, 3,420,899 1/1969 Longiave 61 al. ..260/666 3,496,129 2/1970 Wismer et a] ..260/666 [22] Filed: March 22, 1971 3,567,792 3/1971 Bozik et a1 ..260/677 [21] Appl. No.: 126,9 Primary Examiner-Delbert E. Gantz Assistant Examiner--C. E. Spresser 52 U.S. c1. .....260/666 A, 260/666 B, 260/666 PY, rworth and Henry Geller 260/677 R, 260/680 B, 260/683.15 D 51 1 I111. Cl. "@3076 13/28, C07C 13/06 [571 CT [5 8] Field of Search ..260/666 A, 666 B, 677 R, v l bum s are prepared by cyclocodimerizing 680 B,260/683.l5 D

a diene and a monoolefin, in liquid phase solution, in the presence of a catalyst system containing an or game-titanium compound.

7 (Dis, N0 Drawings I CYCLODIMERIZATION PROCESS olefins by homogeneous transition metal complexes have been studied extensively since'the early 1960's.

Such catalystsoffer the possibility of achieving product typesand product selectivities previously unobtainable byconventional acid'or base catalysis. The unsaturated products of the indicated olefin conversion processes may be further transformed to industrially useful polymers and'functional derivatives.

Until recently, the above-identified olefin conversion processeshave not been applied to the synthesis of vinylcyclobutanes, which are useful as starting materials in the preparation of coand homo-polymers, nematocides and perfumes.

Preparation of vinylcyclobutane itself has followed classical methods of organic systhesis. Vogel et al. (Ann., 615: 29, 1958) prepared vinylcyclobutane in low yield by the 1,2 addition of ketene to butadiene, with subsequent Wolf-Kishner reduction of the vinylcyclobutanone. Overber'ger et al. (J. Polymer Sci., Part A, 2': 755, 1964) have disclosed an improved-yield preparation involving some seven steps. Recently, Bartlett et al. (J.A.C.S., 90: 6071, 1968) found that the addition product of ethylene and butadiene at 175C and 6,000 psi consisted of 99.98 percent cyclohexene and 0.02 percent vinylcyclobutane.

Montacatini Edison, Belgian Pat. No. 750,288 (issued Nov. 12, 1970) disclose the formation. of vinylcyclobutanes by reacting bicyclo(2.2.l)hepta-2,5- diene with either 1,3 butadiene or isoprene in the presence of a ternary catalyst system comprising (a) an iron compound, (b) an ether or phosphine, and (c) an organo-aluminum or organo-magnesium compound.

ln-view of the attractive nature of vinylcylobutanes as organic intermediates and polymerizable monomers and the fact that classical methods of preparation are cumbersome and relatively uneconomical, the need for a simple preparative technique, which employs readily available and comparatively inexpensive precursors, is

apparent.

' SUMMARY OF THE INVENTION It has now been found that C -C straight chain conjugated dienes and certain monoolefins are cyclocodimerized in liquid phase solution to yield vinylcyclobutanes with a catalyst system comprising an organo-titanium compound.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A. The Organo-Titanium Catalyst The titanium catalyst is an organo-titanium compound wherein the titanium in the reaction system has an apparent oxidation state no greater than IV. In one modification of the invention, suitable titanium catalysts comprise those compounds represented by the formula R.,Ti (I wherein each R independently isa monovalent radical such as methyl, allyl, phenyl, benzyl or cyclopentadienyl, with the proviso that no more than one R sub- 2 stituent is cyclopentadienyl. Illustrative of such hydrocarbyl organd-titanium compounds are 'tetrabenzyltitanium," tetraphenyltitanium, cyclopentadienyltitanium tribenz'yl, cyclopentadienyltitanium trimethyl, cyclopentadienyltitanium triphenyl, dimethyldibenzyltitanium and triphenylbenzyltitanium.

In a second modification of the invention, the catalyst is a two-component catalyst comprising (1) an organo-titanium compound wherein the titanium is in an apparent oxidation state of III or IV and (2) a hydrido, aryl or alkyl derivative of at least one metal of Group IA, 11A or IIIA of the Periodic Table.

In this secondmodification employing a two-component catalyst, organo-titanium compounds suitable utilized as catalyst components are represented by the formula S Ti n wherein S independently is (a) alkoxy or aryloxy of up to 10 carbon atoms, (b) chlorine or bromine, or (c) R, where R has the previously stated significance. Thus, the titanium component of the two component catalyst system is a compound of formula (I) above,a tetraalkyl titanate ester such as tetrabutyltitinate, tetrae'thyltitinate, tetrapropyltitinate or dimethyldioctyltitinate, or a halogen-containing material such as, for instance, cyclopentadienyltitanium trichloride.

Suitably employed as the second component of the two component catalyst are metal hydrides such as lithium aluminum hydride, sodium hydride, calcium hydride and potassium hydride; metal alkyls including n-butyl lithium, diethyl magnesium, octyl sodium, and triethyl aluminum; and metal aryls illustrated by phenyl sodium, phenyl lithium, and cyclopentadienylaluminum diethyl. Preferred as the second catalyst component are aluminum hydrides, aluminum alkyls'and alkyl aluminum hydrides of up to.8 carbon atoms in each'alkyl group. v

In the two-component catalysts of the invention, the ratio of titanium compound (1) to Group I-IIIA metal compound (2) is not critical, although molar ratios from about 0.5:1 to about 1:10 are suitable. Molar ratios in the higher end of the indicated range, i.e., 1:6-10, are advantageously employed when the titanium component contains one or more halogen substituents. 5

In either modification of the catalysts of the invention, additional catalyst modifiers are on occasion usefully employed. Such catalyst modifiers comprise stabilizing ligands such as amines, phosphines, stibenes, arsines, ethers and the like. Bidentate amines of the pyridine type are particularly preferred catalyst modifiers. In some instances, the modifier, which may be soluble or insoluble, is present in substantial quantities, e.g., up to about moles per mole of titanium compound, and serves as the reaction-diluent as well as the catalyst modifier. In many cases, however, no more than minor amounts, e.g., amounts equimolar with the titanium compound, are employed, and in most instances, no catalyst modifier is employed.

B. The Ethylenic Reactant The ethylenic reactant comprises ethylene and certain hydrocarbon substituted ethylenes wherein the carbon-carbon double bond is activated or rendered more available for reaction by inclusion within a Diels Alder adduct containing at least two carbocyclic rings, at least one of which has no more than 5 carbon atoms in the ring and contains a carbon-carbon double bond. Genetically, such ethylenic reactants are characterized by the formula wherein X independently is hydrogen or both X substituents together form a divalent radical selected from reaction of the present invention proceeds may be varied over a wide range. It has been found that the reaction proceeds satisfactorily at temperatures from about 80 to about 200C. Preferably, the cyclocodimerization is conducted at from about 130 to about 170C.

The pressures employed may vary from ambient to as much as 2,000 psi or more, and will in part depend upon the amount and volatility of the mono-olefinic and diene organic substrates which are present, since the reaction is conducted in the liquid phase. The preferred range of operating pressures lies between about 200 and about 1,500 psi.

. It is desirable to conduct the cyclocodimerization in the presence of an organic diluent which does not adversely affect the cyclodimerization reaction. Representative of these diluents are aromatic hydrocarbons such as benzene, toluene, and xylene, and aliphatic hydrocarbons such as hexane, heptane, pentane, and isopentane. Other types of organic diluents, e.g., ethers such as tetrahydrofuran, 1,2- dimethoxyethane and dioxane, are also suitably employed as solvents and additionally function as catalyst modifiers.

The ratios of monoolefinic and diene reactants with respect to the titanium catalysts are variable. Generally, per mole of titanium in the cyclocodimerization reaction mixture, it is desirable to have from about 90 to about 1,000 moles of monoolefin and from 90 to about 300 moles of diene. Preferably, the molar ratio of titaniumzmonoolefin: diene is l:90-600:90-200. The amount of total unsaturated reactant, i.e., monoolefin plus diene, suitably lies within the range of about 400 to about 1,200 moles per mole of titanium cyclocodimerization catalyst. Preferably, from about 400 to about 800 moles of total unsaturated reactant per mole of titanium is employed in forming vinyl cyclobutane. Generally, it is preferable to have the monoolefin in excess, particularly where the monoolefin is ethylene.

The cyclodimerization is conducted .by contacting the reactants and catalyst in the reaction diluent in the liquid phase. Such contacting can be effected batchwise or in a continuous manner and the entire amounts of reactants are initially mixed or one reactant can be added to the remaining reaction mixture components in increments.

Subsequent to reaction, the product mixture is separated and the vinylcyclobutane product is recovered by conventional means, e.g., fractional distillation, selective extraction and gas-liquid chromatographic techniques.

Vinylcyclobutane products result from cyclocodimerization of the ethylenic and diene reactants. Illustrative of such products are vinylcyclobutane produced from reaction of ethylene and butadiene,

vinylmethylcyclobutane produced from ethylene and piperylene and 3-vinyltricyclo( 4.2. l .0- )nonaneproduced by reaction of butadiene and bicyclo(2.2.l)hept-2-ene.

The vinylcyclobutane products as such, or in an isomerized configuration, are useful as monomeric sub strates for high molecular weight polymers. For instance, vinylcyclobutane has been polymerized by Overberger et al. (J. Polymer Sci., Part A, 2: 755, 1964).

EXAMPLES With the exception of run 153 in Example 111, all of the cyclocodimerizations were carried out in an 84 ml autoclave equipped with a magnetic stirrer. Argon was used to sweep the autoclave before loading with monoolefins and dienes.

Where a Group I-IIIA organo-metallic compound formed a part of the catalyst system, this material was generally added to the diluent or a mixture of diluent and the organo-titanium compound, with mixing at 0C, and then the diene and monoolefin substrates were added.

Where three values are reported for the temperature employed during a single run, these correspond to the initial temperature, the maximum temperature which was achieved due to the exothermisity of the cyclocodimerization, and the final temperature. Similarly, where two pressures are reported for an individual run, these correspond to the maximum and final pressure recorded.

In the tables which accompany the examples, the following abbreviations are employed:

I. Titanium Materials (n-CJLO Ti tetra-n-butoxytitanium C H Ti(CH Ph) cyclopentadienyltitanium tribenzyl (AcAc),TiO titanylacetylacetonate C l-l TiCl cyclopentadienyltitanium trichloride 11. Second Component of Two-Component Catalyst System Et Al triethylaluminum n-CJ-I Li n-butyllithium LiAll'L, lithium aluminum hydride a z a elhulalumtmm :erqutcltlartde Ill. Catalyst Modifiers i.e., Stabilizing Ligands Bipy 2,2'-bipyridyl Ph P triphenylphosphine Py pyridine Phen 1 1 O-phenanthrolene The solvent employed in the cyclocodimerization of the present invention is not limited to hydrocarbons, but may include other types of organics, such as tetrahydrofuran, 1,2-dimethoxyethane, and dioxane, as

TMEDA tetramethylenediamine 5 shown in runs 123, 124, and 167, respectively.

TABLE 1 l1nhulloim-Ethy1on0 Uyclocmllmnrlzntion with (lilli'llfl/lizlhh ltun 40 03 61 71 60 ltuuctnnls:

'11, IIIIIIOlHH. 0. 75 1.12 1.12 1.12 1.12 llntiidlcno, 13.. 10.3 7. 0. 0 15.6 7.1 Ethylene, 11.. 2. 11. 5 14.0 2. 5 18.0 Reaction conditions:

Dnrntlon, hrs... 1. 17 0. 1.0 3 0.5 '1mnporntui'c, (3... 150/100/135 135/1110/1 10 135/1110/135 155/1110/175 138/156/132 Pressure, 11.8.1.1!" 380/242 1,021/1, 0011 1,200/1, 1112 004/520 1,088/1, 370 Approximate conversion, percent:

Butudienc. -00 -80 -86 -00 J0 -38 -10 -13 8 2. 0 s 5.1 2.4 15. 7 33.3 48 04. 2 33.5 42 49. 0 40 25. 1 431 8 37 g. 1 a 3.2 10.0 a

. 9 0. 3.7 1 2.1 1 Ca olefins, percent w.:

Ethylene trimer 0. 7 3. .1 4. 0 1. 2 7. 5 Vinylcyclobutane 23. 9 38. 2 28. 8 47. 0 47. 4 Hexadienes 44. 3 45. 5 45. 0 37. 0 35. 5 Ethyideneeyclobutano. 31. 1 11. 1 20. 7 8.2 7. 9 Others 1. 3 0. 9 5. 7 1. 7

" Gas chromatography of 04-020 liquid product. b Minutes.

EXAMPLE I. Butadiene-Ethylene Cyclocodimeriza- TABLE H tion with CyclopentadienyLTitani Trib l 30 Butndiene-Bicyelic Olefin Cyclocodimerization with C5HiTi(CH Ph)i Varying amounts of 'cyclopentadienyltitanium mm 143 145 146 tribenzyl were mixed with butadiene and ethylene in 10 Reacmnts. ml of toluene, and the reaction was permitted to T1, mmo1es 1.0 1.0 1.0 Butadiene, g. 14.0 14.0 14.0 proceed for varying amounts of tlme. Reaction condltions, quantities of reactants and conversions and 'selec- Olefin tivities, as determined by gas-liquid chromatographic I l I l (GLC) analysis, were reported in Table 1. Analysis for the C olefins were confirmed by hydrogenation of this fraction over Raney nickel at 100C, under which con- 0 None None Toluene d1t1on vinylcyclobutane was converted to ethylcyclobu- 40 1mm, ml 10.

Reaction conditions: tane'. Duration, hrs. 1.0 EXAMPLE 11. Butadiene-Bicyclic Clefin Temperature. 0 134-138 Pressure, p.s.1.g. 280/35 280/108 220/116 Cyclocodlmenzation with Cyclopentadienyl-Titanlum percent;

Tribenzyl gf i e n Monolefinic materials other than ethylene may be lec i y, W":

Cyclobutane codlmcr 40 67. 5 46. 1 cyclocodunenzed w1th a diene. Thus, when butadlene 1c c101iexene-1 10.1 13.5 30.3 is reacted with a strained bicyclic olefin such as $3. m? gl bicyclo(2.2.1)hepa-2,5-diene or bicyclo(2.2.1)hept-2- C High b i ers 20.0 16.0 13.0

. C911 W-I ene high y1elds to the C polycyclic codnners, per identified by nuclear magnetic resonance (NMR), were 2 achieved. Details of such cyclocodimerizations were shown in Table II. EXAMPLE III. Butadiene-Ethylene Cyclocodimerizations in the Presence of Tetra-n-butoxytitani- 05.0 um/Triethylaluminum In a series of runs detailed in Table III, butadiene and ethylene were cyclocodimerized to vinylcyclobutane by a catalyst system consisting of tetra-n-butoxytitaniot g g 344) 16,8 Um and trlethylalummum. The l'eactlon was effected m other 011E165 the presence and absence of various stabilizing ligands. 4 Via distillation.

N2 3 3 m4 9m 2. Mg 9w N m4 J iawfio 2 a Z 3 Z 2 a c Q 3 n un wawwmm ua w 9% 5 M13 in Q8 mi 35 9m 95 3 H H H H .H H.H.H.HEH... EEGQWE 5 2: :5 mg mam v 3 T3 98 0 2 nan .w 2 o 3 92 Z 92 w 1: 55: 32.56 .3 363mm ccgwonaou 32 5 E Q m m c n ma o w ....1.....1..........L,.l....mEm damage M BEBQ QE 2. 2 68mm mu g c g 25% 2 5 N 3. w w a c v 1n n E w m w Pm a 9m m4 Q w; H w 3. w w 2 N 2 m 2 Q 2 o 2 w 2 mm 2 o 2 N. v W$$E$$$E N ow is 9E mi 9: NE E a mi 3 H Wm.HMLHHPPPPPH,..H....::-..H m6 2 Q2 2 g in Z x a 2 on mwim =5 E533 fi w $3 2 D 2 a E 8 2 mm a H H H H wnHHH HHAHNHHHHHHHnnHHHHHHHW 3 a 2 2 me E 2 3 8 8 222:5 wimp-0Q CA ZwHQNZhOU QQQMMHEMOkQQA gm H miiwmmx wwoifiwq BR imzl STQNMNJ owmifim; c3435; mhmigwa c3482; Wwmd wmfim E e: =2 O2 Q2 Q2 .5 Q3552 w- 2 Q2 wzhfisfi l name 8 M i a: A: m6 a 2. nd n6 n6 m2 555:9 HmGOGHUCOU SOUQQQMH 25 H 2 2 2 2 cm 2 2 2 2 HHHHHMHHHWMHHHMH 2 2 258 25 5 @5 @5 2 5 052 262 2629a w Em mi 92 :2 92 9: E 52 2: wfi U H WUHHHmwHHHHMHUHHMHWNMMPH: Salim 2% o c n ms n m5 n n ms .H 0568mm 2 i 3 3 Z 2 ma 5 H EP 55m 5 -33 E G 2 3 2 2. 2 2 2 3 2 2 n AH HnHMHHHH H.H.wwvflhwwa E z o; A: .2 4 A: o 0; ca 6 5. 5223mm E n: *2 E N: O: m2 2: 2: E :E SM P2QW6AC an cofis waaooom nu ummafimcflufism H: mHAm B IOIC54 Run 153 proceded in a one gallon autoclave. The triethyl aluminum was added to a toluene solution of the tetrabutyltitinate and the 1,10-phenanthro1ine at below C. The reactive organic substrates were then period the maximum and final pressures were 1,288 and 1,120 psig, respectively. Under these conditions the pentadiene and ethylene conversions were 40 and 19 percent, respectively. Selectivity to butenes was added, and the reaction allowed to proceed. As in the to 1 Was and 10 was The previous two Examples, the composition of the C frac major olefinic products were separated by gas chrotion was verified by hydrogenation. matography and identified by NMR as cisand trans-2- EXAMPLE 1V. Butadiene-Ethylene Cyclocodimerizamethyl-vinylcyclobutane and 3-methyl-1-cis-4-hextion by Tetrabenzyltitanium adiene. After the product had been hydrogenated, gas Tetrabenzyltitanium is representative of other orchromatography, alone or in combination with mass gano-titanium compounds which catalyze the spectral analysis, revealedthe following weight comcyclocodimerization of a diene with a monoolefin. positions: 52 percent 2-methyl-1-ethylcyclobutanes When 1.0 mmole of tetrabenzyltitanium and 1.0 mili n 1 percent 3-methylhexene. 2 p n limoles of 2,2-bipyridyl, dissolved in milliliters of l 5 n-hep ane, 3 percent methylcyclohexane, and 12 pertoluene, were mixed with 7.0 grams of butadiene and Cell! fiable- 11.5 grams of ethylene, cyclocodimerization was ef- MPL fected for a period of 2.0 hours at a temperature of A modified titanium catalyst component, prepared 140 to 150C. The maximum and final pressure obby reacting tetra-butyltitanate with 8-hydroxyquino1ine served during this reaction were 1,016 and 982 psig, 20 (13%w titanium and 5.5%w nitrogen by analysis), was respectively. Butadiene and ethylene conversions durused as a catalyst precursor. In 10 ml of toluene, 0.41 ing this period were 79 and 18 percent, respectively. grams of the titanium chelate and 2.5 mmoles of Selectivities to butenes, C s,4-viny1cyc1ohexane1, triethylaluminum were dissolved. To the catalyst-conother C,,, and polymers were 4.3, 64.0, 14.5, 2.5 and taining solvent were added 8 grams of butadiene and 16 14.7 percent by weight, respectively. An analysis of the grams of ethylene. The cyclocodimerization was a1- C olefin fraction indicated 2.5%w ethylene trimer, lowed to proceed for approximately minutes at a 72.8%w vlnylcyclobutane, 20.8%w hexadienes, atrace temp rature of 146 to 148C. After isolation and of ethylidene cyclobutadiene, and 3.9 percent heavier hyd gena o of e a olefin ra ga chromatogmaterials, respectively. Under roughly equivalent reacp y Indicated a conten of 49.3 percent ethyltion conditions, but in the absence of an added ligand, 30 eyelobutane. percent n-hexane, a -5 percent 3- the C selectivity was only 24.0%w, the polymer make methylpemanewas 47.4%w, and the vinylcyclobutane present in the EXAMPLE 1 Butadlene'Ethylene cyclocodlmel'iza- C l fi fr ti a 45,1% tions Employing Various Two-Component Catalyst EXAMPLE V. Cyclocodimerization of Pentadiene and Systems Ethylene Butadiene and ethylene were cyclocodimerized to To 1.5 millimoles of cyclopentadienyltitanium vinylcyclobutane with a variety of two-component tribenzyl dissolved in 5 ml of n-nonane were added catalyst systems shown in Table IV. As shown in run 13.4 grams of 1,3-pentadiene and 12.0 grams of 103, a higher molar ratio of reducing agent to titanium ethylene. Cyclocodimerization was allowed to proceed compound is employed when the latter contains for 0.5 hours at a temperature of 150C, during which 40 halogen substituents.

TABLE 1v Butadiene-Ethylene Cyeloeodimerizatlon With Various Two-Component Catalyst Systems Run 91 81 74 102 103 Reactants:

'Ii Catalyst (n-cilriowri (n-oilnomi (n-cimon'ri (AeAehTiO C5H5T1C1 Mmoles 1.0 1.5 1.0 1.0 1.0 Reducing agent. nC1II L1 Et1AlgCl1+Et3Al L1A1II4 EtaAl EtaAl Mmoles... :1. 0 1. 0, a. 15 0. 05 7. 5 7.5 Butadiene, g 8. 5 8.0 8.5 8. 0 7. 0 Ethylene, g. 13. 2 12. 5 17. 5 12. 0 9. 5 Solvent THF Toluene 'IHF 'IHF THF M1 10 10 10 10 Reaction conditions:

Duration, l1rs 1. 5 17 4. 3 1. 76 0.25 Temp. range, 0 110150 1115-150 -150 150-114 -150 Press, p.s.i.g 1,100 1,150 1,224/1,048 1,800/1,624 1,230/1,205 1,005 1,043 Approximate conversion, percent:

Butadiene 00 88 62 91 86 12 10 5 10 1s 51 1 1.4 7.5 17 1s 50 68.5 54 17 32 27 22 15 14 11 15.5 2 4 Polymer (solid) 0 6 11 0 0 Butadiene as high molecular weight oligomer, g 7. 0 0.8 0 5 O5 olefin composition, percent w.:

Ethylene trimer 33 1 1 5. 8 2. 9 Vinylcyclobutane 18 37 12 60. 3 31. 3 1,4-hexadiene 22 38 27 28. 7 Trace Ethylidenecye1obutane.. Trace Trace 0. 3 43. 4 Cyelohexaene 27 21 2.6 0. 15 2,4 hexadienos and others 1 3 1 2. 3 12. 7

(111s(111mmntogmphy of (1 41 11( 11111 product. May be low (1110 to 1111111111111: losses. 'lllermnl, 1 1o1s-A111or dimer. 'Illermul product.

I claim as my invention:

1. A process for producing vinylcyclobutanes by cyclocodimerization which comprises contacting an ethylenic reactant selected from ethylene and ethylenic Diels-Alder adducts of at least two carboxylic rings, at least one of which has no more than five carbon atoms and contains a carbon-carbon double bond, with a C -C straight-chain hydrocarbon conjugated alkadiene, in liquid phase solution in the presence of a titanium catalyst having an apparent oxidation state no greater than IV, said catalyst being selected from a. titanium compounds of the formula wherein R independently is methyl, allyl, phenyl, benzyl or cyclopentadienyl, with the proviso that no more than one R is cyclopentadienyl, and b. two component titanium catalysts comprising 1. titanium compounds of the formula wherein S is (a) alkoxy or aryloxy, (b) chlorine or bromine, or c. R as previously defined, and

metal of Groups lA, IIA, or 111A of the Periodic Table is triethylaluminum.

6. The process of claim 1 wherein the cyclocodimerization is conducted in the additional presence of titanium catalyst modifiers comprising stabilizing ligands.

7. The process of claim 6 wherein the stabilizing ligand is selected from the group consisting of 2,2- bipyridyl and 1 l O-phenanthrolene. 

2. hydrido, alkyl or aryl derivatives of at least one metal of Groups IA, IIA or IIIA of the Periodic Table.
 2. The process of claim 1 wherein the ethylenic reactant is selected from the group consisting of ethylene, bicyclo (2.2.1)hepta-2,5-diene, bicyclo-(2.2.1)hept-2-ene, and tricyclo(5.2.1.02,6)deca-3,9-diene.
 3. The process of claim 1 wherein the C4-C5 straight chain hydrocarbon conjugated alkadiene is butadiene.
 4. The process of claim 1 wherein the cyclocodimerization proceeds in the presence of an organic diluent selected from the group consisting of aromatic and aliphatic hydrocarbons and ethers.
 5. The process of claim 1 wherein said derivative of a metal of Groups IA, IIA, or IIIA of the Periodic Table is triethylaluminum.
 6. The process of claim 1 wherein the cyclocodimerization is conducted in the additional presence of titanium catalyst modifiers comprising stabilizing ligands.
 7. The process of claim 6 wherein the stabilizing ligand is selected from the group consisting of 2,2''-bipyridyl and 1,10-phenanthrolene. 